linux下ls.c編寫

/********************
data:2010-11-22
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#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <grp.h>
#include <pwd.h>
#include <string.h>

void do_ls(char[]);  //讀取目錄中的基本文件信息
void dostat(char *); //獲得STAT結構
void show_file_info(char *, struct stat *);  //顯示文件信息
void mode_to_letters(int, char[]);  //int型模式轉換成string模式
char *uid_to_name(uid_t);
char *gid_to_name(gid_t);

int main(int argc, char *argv[])
{
    if (argc == 1)
        do_ls(".");
    while (--argc)
    {
        printf("%s:/n",*++argv);
        do_ls(*argv);
    }
    return 0;
}

void do_ls(char dirname[])
{
    DIR *dir_ptr;
    struct dirent *direntp;

    if ((dir_ptr = opendir(dirname)) == NULL)
        fprintf(stderr,"ls:cannot open %s/n",dirname);
    else
    {
        while ((direntp = readdir(dir_ptr)) != NULL)
            dostat(direntp->d_name);
        closedir(dir_ptr);
    }   
}

void dostat(char *filename)
{
    struct stat info;
   
    if (stat(filename,&info) == -1)
        perror(filename);
    else
        show_file_info(filename,&info);
}

void show_file_info(char *filename, struct stat *info_p)
{
    char modestr[11];

    mode_to_letters(info_p->st_mode,modestr);
    printf("% s",modestr);
    printf("% 4d ",(int)info_p->st_nlink);
    printf("% -8s ",uid_to_name(info_p->st_uid));
    printf("% -8s ",gid_to_name(info_p->st_gid));
    printf("% 8ld ",(long)info_p->st_size);
    printf("% .12s ",4+ctime(&info_p->st_mtime));
    printf("%s/n",filename);
}

void mode_to_letters(int mode,char str[])
{
    strcpy(str,"----------");
   
    if (S_ISDIR(mode)) str[0] = 'd';
    if (S_ISCHR(mode)) str[0] = 'c';
    if (S_ISBLK(mode)) str[0] = 'b';

    if (mode & S_IRUSR) str[1] = 'r';
    if (mode & S_IWUSR) str[2] = 'w';
    if (mode & S_IXUSR) str[3] = 'x';

    if (mode & S_IRGRP) str[4] = 'r';
    if (mode & S_IWGRP) str[5] = 'w';
    if (mode & S_IXGRP) str[6] = 'x';

    if (mode & S_IROTH) str[7] = 'r';
    if (mode & S_IWOTH) str[8] = 'w';
    if (mode & S_IXOTH) str[9] = 'x';

}

char * uid_to_name(uid_t uid)
{
    struct passwd *pw_ptr;
    static char numstr[10];
   
    if ((pw_ptr = getpwuid(uid)) == NULL)
    {
        sprintf(numstr, "%d", uid);
        return numstr;
    }
    else
        return pw_ptr->pw_name;
}

char *gid_to_name(gid_t gid)
{
    struct group *grp_ptr;
    static char numstr[10];

    if ((grp_ptr = getgrgid(gid)) == NULL)
    {
        sprintf(numstr,"%d",gid);
        return numstr;
    }
    else
        return grp_ptr->gr_name;
}